Engineering topics

Shumpert, Thomas H.

Publications and source records attributed to Shumpert, Thomas H..

5 records

NASA NTRS2016

Measurement of Antenna Bore-Sight Gain

The absolute or free-field gain of a simple antenna can be approximated using standard antenna theory formulae or for a more accurate prediction, numerical methods may be employed to solve for antenna parameters including gain. Both of these methods will result in relatively reasonable estimates but in practice antenna gain is usually verified and documented via measurements and calibration. In this paper, a relatively simple and low-cost, yet effective means of determining the bore-sight free-field gain of a VHF/UHF antenna is proposed by using the Brewster angle relationship.

Fortinberry, Jarrod↗

NASA NTRS1991

A simulated lightning effects test facility for testing live and inert missiles and components

Details of a simulated lightning effects test facility for testing live and inert missiles, motors, and explosive components are described. The test facility is designed to simulate the high current, continuing current, and high rate-of-rise current components of an idealized direct strike lightning waveform. The Lightning Test Facility was in operation since May, 1988, and consists of: 3 separate capacitor banks used to produce the lightning test components; a permanently fixed large steel safety cage for retaining the item under test (should it be ignited during testing); an earth covered bunker housing the control/equipment room; a charge/discharge building containing the charging/discharging switching; a remotely located blockhouse from which the test personnel control hazardous testing; and interconnecting cables.

Craven, Jeffery D.↗

NASA NTRS1991

Backscatter RCS for TE and TM excitations of dielectric-filled cavity-backed apertures in two-dimensional bodies

Transverse electric (TE) and transverse magnetic (TM) scattering from dielectric-filled, cavity-backed apertures in two-dimensional bodies are treated using the method of moments technique to solve a set of combined-field integral equations for the equivalent induced electric and magnetic currents on the exterior of the scattering body and on the associated aperture. Results are presented for the backscatter radar cross section (RCS) versus the electrical size of the scatterer for two different dielectric-filled cavity-backed geometries. The first geometry is a circular cylinder of infinite length which has an infinite length slot aperture along one side. The cavity inside the cylinder is dielectric filled and is also of circular cross section. The two cylinders (external and internal) are of different radii and their respective longitudinal axes are parallel but not collocated. The second is a square cylinder of infinite length which has an infinite length slot aperture along one side. The cavity inside the square cylinder is dielectric-filled and is also of square cross section.

Goggans, Paul M.↗

NASA NTRS1991

A new surface impedance function for the aperture surface of a conducting body with a dielectric-filled cavity

A surface impedance function (SIF) appropriate for use on the aperture surface of a conducting body with a dielectric-filled cavity, is presented. Unlike the usual SIFs that might be used on an aperture, this SIF takes into account not only the wave transmitted through the aperture but also the wave reflected from the inside of the cavity the shape of the aperture and cavity, and the polarization and direction of the incident wave. The SIF is derived heuristically from the series-reflection solution for a plane wave normally incident on an infinite flat conducting plate with a flat dielectric coating. The SIF was developed and used in a combined method of moments (MM) solution for the scattered fields due to an incident plane wave. This combined technique greatly reduces the number of current expansion coefficients to be determined using the method of moments and hence also reduces the number of impedance elements required for calculation in the method of moments. Application of the SIF in a combined method is illustrated for a two-dimensional object.

Goggans, Paul M.↗

NASA NTRS1990

CFIE MM solution for TE and TM incidence on a 2-D conducting body with dielectric filled cavity

The problem of determining the scattering cross section of an arbitrarily shaped two-dimensional conducting body with an arbitrarily shaped dielectric-filled cavity is considered. The problem is solved using a method-of-moments (MM) solution for the combined field integral equations (CFIE). The particular form of the method of moments solution used has here uses a minimum number of expansion coefficients. Results are given for TE and TM incident waves.

Goggans, Paul M.↗